Tip #3 "Second-hand first"
This tip is very simple, but maybe feels hard in the beginning, depending on the facilites in your country:
If you think of items that you need and want to buy, ALWAYS first look second hand! There are several platforms online, both national and international, where people exchange stuff for a low bid or even free. And in many countries, you will even find smaller and and bigger thrift stores, where you can find these items. Of course, you still need to check the consdition and quality. But that is what you would do on a "regular" shopping trip anyways, right?
Example: Personally, I find it fun to set a date once in a while for searching 3-5 thrift stores in my area for anything I am still missing. (See list from tipp #1.) I keep it short, search focused for item X and then at the end of the day buy it or leave it. In my opinion, that is about the same effort, or less, when doing a "regular" shopping trip.
TL;DR: Search for your wanted items in second-hand stores or online marketplaces. Often you find what you need, in still good condition and cheaper. Also you give these items a longer life. And the effort is similar/lower to "new shopping" if you do it focused.
It is often cheaper and the pre owner give you sometimes tips and accesories.